Control System I/O Wiring

[tech_coord]

Can conductors for 24 vdc interrogated inputs and 120 vac or 125 vdc powered outputs be contained in a common multiconductor cable? The I/O is located in a distributed control system (DCS) cabinet and the input interrogation power is derived from the DCS. The outputs are powered from a combination motor starter control power transformer in a motor control center or from a 125 vdc control power bus in a metal clad switchgear breaker compartment. It is unclear to me if these circuits would be categorized as class 2 or 3 circuits under Article 725 or if they fall solely under Article 300.

[ March 11, 2005, 03:19 PM: Message edited by: tech_coord ]

 

[rbalex]

Re: Control System I/O Wiring

Class 2 & 3 circuits are defined in terms of their power supply. See 725.2. If the "power supply" isn't Class 2 or 3, the ciruit isn't.

 

[tom baker]

Re: Control System I/O Wiring

They may be a class 1 power or non power limited remote control and signaling circuit. Take a look at ARt 725 Part II.